This invention relates to drain constructions located in the bottom or along the sides of a pool or hot tub through which water flows under the action of gravity or a pump that acts to suck water out of the pool.
The dangers inherent in pools and hot tubs having circulating water systems are well known and documented. For example, suction or vacuum forces frequently occur near the water drains sufficient to hold a swimmer or user in life threatening situations. Entanglement or knotting of hair on or through a sump, suction line or a drain grate can also cause injuries and possibly drowning.
Limbs can be inserted into suction lines, such as PVC pipes, when the suction fittings or covers are removed or missing from a sump. Suction can draw the limbs into the pipes fitted to the sumps; here the limbs can be trapped by suction, friction, swelling of the limb, etc.
A homemade remedy for the limb entrapment hazard is to insert a couple of cross bolts in a simple pattern at the entrance to the pipe. Bathtub drains and slop sink drains adopt this concept. Some drain lines use manufactured perforated covers. These concepts generally introduce a hair entrapment hazard. They can also give rise to a mechanical finger entrapment hazard. Furthermore, they allow a hand to seal off a small pipe (2″ to 3″ diameter) and instantly develop close to the theoretical vacuum limit (14.7 psi). A three inch PVC pipe can develop nearly 100 lbs of holding force on a bather.